<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Task 2-22</title>
    <link rel="stylesheet" href="css/style.css" />
</head>
<body>
<section class="wrapper level0">
    <div class="left-child level1">
        <div class="left-child level2">
            <div class="left-child level3"></div>
            <div class="right-child level3"></div>
        </div>
        <div class="right-child level2">
            <div class="left-child level3"></div>
            <div class="right-child level3"></div>
        </div>
    </div>
    <div class="right-child level1">
        <div class="left-child level2">
            <div class="left-child level3"></div>
            <div class="right-child level3"></div>
        </div>
        <div class="right-child level2">
            <div class="left-child level3"></div>
            <div class="right-child level3"></div>
        </div>
    </div>
</section>
<button>前序遍历</button>
<button>中序遍历</button>
<button>后序遍历</button>
<script src="js/util.js"></script>
<script src="js/task.js"></script>
</body>
</html>